20hp merc. Runs good, stalls then runs good

[sgms18]

I have an older 20hp merc tiller steer. The serial number is gone so I have no way of knowing exact year. If I had to guess Id say late 70s early 80s, Black w/blue band around the cover and it says "thunderbolt ignition system" on the front cover. Ok, the problem. It will start up and run great from idle to wide open sometimes 10-15min sometimes an hour then it stalls. It starts right back w/a pull or two of the rope and runs great. Stalling always happens when im running wide open. Any ideas? Also, if I leave the motor up on the latch (which I must to keep the foot from draging the ground when trailering) fuel leaks from the carb. It dosen't seem to happen when the motor is in the upright running position. Is this normal? I really appreciate any help yall can give!

 

[Wingedwheel]

Re: 20hp merc. Runs good, stalls then runs good

The fuel leaking from the carbs is normal. It pours out the front of the carb when tilted up. As for the stalling problem, when is the last time you serviced your carbs? It could have some trash floating around in the bowl if you run it without a fuel filter.

 

[Maxz695]

Re: 20hp merc. Runs good, stalls then runs good

carbs are a good possibility might ans well do the fuel pump while your at it

 

[sgms18]

Re: 20hp merc. Runs good, stalls then runs good

I have had the boat bout 6 months and I have no idea if/when the carb has been serviced. Any idea how I could find the right rebuild kits w/out the serial number or knowing what year it is?

 

[RiverKnight]

Re: 20hp merc. Runs good, stalls then runs good

I can tell u right now all you need is tp get the carbs new gaskets ,spring and diaphragm abd you'll be good just had a stalling problem and that fixed my problem , check my other thread...another thing if you not doing it yourself be sure and take it to a big Marine Service Center and pay the money save the headache..

 

[sgms18]

Re: 20hp merc. Runs good, stalls then runs good

i can tell u right now all you need is tp get the carbs new gaskets ,spring and diaphragm abd you'll be good just had a stalling problem and that fixed my problem , check my other thread...another thing if you not doing it yourself be sure and take it to a big marine service center and pay the money save the headache..

huh???

 

[Mi duckdown]

Re: 20hp merc. Runs good, stalls then runs good

RiverKnight What?

 

[Mi duckdown]

Re: 20hp merc. Runs good, stalls then runs good

There should be a number on the welch plug, that will give you exact year of that motor.

 

[sgms18]

Re: 20hp merc. Runs good, stalls then runs good

There should be a number on the welch plug, that will give you exact year of that motor.

There are no serial numbers anywhere on this motor. Looked at freeze plugs, welch plug, block, lower unit, just a few part numbers here and there. I took it to the local marina they coludn't find it. Neither could the "marine investigations" guy SCDNR sent to the house to look it over before they would issue me a SN for titeling reasons. Im at a loss. Can I find the year with any of the part numbers? I just need to be able to find parts I dont care what year it is. Is there a range of years where everything interchanges?

 

[Maxz695]

Re: 20hp merc. Runs good, stalls then runs good

i would go to parts and start searching for say spark plugs and what HP and years it falls under the same plug as your engine. Then use that information to match other parts ( Say Carburetor or Flywheel) on your engine to narrow down the year By HP and part numbers. That should give you some kind of clue on the approx SN

 

[sgms18]

Re: 20hp merc. Runs good, stalls then runs good

Well, thanks for all the input yall. I guess im going to try and find the right carb kit and go from there.

 

[Wingedwheel]

Re: 20hp merc. Runs good, stalls then runs good

See if any of these parts look like you're motor. If not, its a good start. http://www.boats.net/parts/search/Merc2/Mercury/20 (2 CYL.)/0B238464 THRU 0G044026/parts.html